404-solution / includes / gsc / GscFetchLock.php

GscFetchLock.php in 404 Solution trunk, at includes/gsc/GscFetchLock.php

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1	<?php
2
3	// allow-no-test-found: exercised by GscFetchPipelineTest contention and migration scenarios
4
5	if (!defined('ABSPATH')) {
6	exit;
7	}
8
9	require_once __DIR__ . '/GscConfig.php';
10	require_once __DIR__ . '/GscFetchLease.php';
11	require_once __DIR__ . '/GscFetchLockStore.php';
12
13	/** Coordinates one renewable GSC fetch lease across requests and upgrades. */
14	final class ABJ_404_Solution_GscFetchLock {
15
16	/** @var ABJ_404_Solution_Logging */
17	private $logger;
18
19	/** @var ABJ_404_Solution_GscFetchLease\|null */
20	private $lease;
21
22	/** @var ABJ_404_Solution_GscFetchLockStore */
23	private $store;
24
25	/** @var int\|null */
26	private $atomicReadyAt;
27
28	/** @param ABJ_404_Solution_Logging $logger */
29	public function __construct($logger) {
30	$this->logger = $logger;
31	$this->store = new ABJ_404_Solution_GscFetchLockStore();
32	}
33
34	/** Initialize and, when absent, persist the atomic-lock migration deadline. */
35	public function initializeAtomicLockMigrationState(): void {
36	if ($this->atomicReadyAt === null) {
37	$this->atomicReadyAt = $this->initializeAtomicReadyAt();
38	}
39	}
40
41	public function claim(): bool {
42	$this->initializeAtomicLockMigrationState();
43	$now = abj_clock()->now();
44	$readyAt = $this->atomicReadyAt === null ? PHP_INT_MAX : $this->atomicReadyAt;
45	if ($now < $readyAt
46	\|\| $this->store->legacyOwner() !== false
47	) {
48	return false;
49	}
50	$value = ABJ_404_Solution_ExclusiveOptionRow::uniqueClaimValue((string)$now);
51	if ($this->store->claim(array('value' => $value))) {
52	$this->lease = $this->atomicLease($value, $now);
53	return true;
54	}
55	$heldSince = $this->store->owner();
56	if (!$this->hasAgedOut($heldSince, $now)) {
57	return false;
58	}
59	$this->store->release(array('value' => $heldSince));
60	$value = ABJ_404_Solution_ExclusiveOptionRow::uniqueClaimValue((string)$now);
61	if (!$this->store->claim(array('value' => $value))) {
62	return false;
63	}
64	$this->lease = $this->atomicLease($value, $now);
65	return true;
66	}
67
68	public function release(): void {
69	if ($this->lease === null) {
70	return;
71	}
72	$this->store->release(array('value' => $this->lease->value()));
73	$this->lease = null;
74	}
75
76	public function isHeld(): bool {
77	if ($this->atomicReadyAt === null) {
78	return true;
79	}
80	$now = abj_clock()->now();
81	if ($now < $this->atomicReadyAt) {
82	return true;
83	}
84	if ($this->store->legacyOwner() !== false) {
85	return true;
86	}
87	$heldSince = $this->store->owner();
88	return $heldSince !== '' && !$this->hasAgedOut($heldSince, $now);
89	}
90
91	public function renewIfDue(): bool {
92	if ($this->lease === null) {
93	return true;
94	}
95	$now = abj_clock()->now();
96	if (($now - $this->lease->renewedAt()) < intdiv(ABJ_404_Solution_GscConfig::LOCK_TTL, 3)) {
97	return true;
98	}
99	$replacement = ABJ_404_Solution_ExclusiveOptionRow::uniqueClaimValue((string)$now);
100	if (!$this->store->renew(array(
101	'currentValue' => $this->lease->value(),
102	'replacementValue' => $replacement,
103	))) {
104	$this->logger->warn('Lost the GSC fetch lock while renewing it; stopping before another API request.');
105	return false;
106	}
107	$this->lease = $this->lease->renewed($replacement, $now);
108	return true;
109	}
110
111	private function initializeAtomicReadyAt(): int {
112	$rawReadyAt = $this->store->atomicReadyAt();
113	if ($rawReadyAt === false \|\| !is_numeric($rawReadyAt)) {
114	$readyAt = abj_clock()->now() + ABJ_404_Solution_GscConfig::ATOMIC_LOCK_MIGRATION_DELAY;
115	if (!$this->store->persistAtomicReadyAt($readyAt)) {
116	$this->logger->warn('Could not persist the GSC atomic-lock migration deadline; GSC fetches remain paused.');
117	return PHP_INT_MAX;
118	}
119	return $readyAt;
120	}
121	return max(0, (int)$rawReadyAt);
122	}
123
124	private function hasAgedOut(string $value, int $now): bool {
125	$timestamp = explode(':', $value, 2)[0];
126	return $value === '' \|\| !is_numeric($timestamp)
127	\|\| ($now - (int)$timestamp) > ABJ_404_Solution_GscConfig::LOCK_TTL;
128	}
129
130	private function atomicLease(string $value, int $now): ABJ_404_Solution_GscFetchLease {
131	return ABJ_404_Solution_GscFetchLease::fromState(array(
132	'value' => $value,
133	'renewedAt' => $now,
134	));
135	}
136	}
137